Here’s a look at seven things you may not have known about daylight saving time.

“Spring forward and fall back” is an easy way to remember how to set the clock when daylight saving times begins and ends. You set your clock forward one hour at 2 a.m. on March 10. You’ll set it back one hour at 2 a.m. on Nov. 3.

In the United States, daylight saving time began on March 21, 1918. U.S. government officials reasoned that fuel could be saved by reducing the need for lighting in the home.

Ancient agrarian civilizations used a form of daylight saving time, adjusting their timekeeping depending on the sun’s activity.

Many people call it daylight savings time. The official name is daylight saving time. No ‘s’ on ‘saving.’

A standardized system of beginning and ending daylight saving time came in 1966 when the Uniform Time Act became law. While it was a federal act, states were granted the power to decide if they wanted to remain on standard time year-round.

Arizona (except for the Navajo, who do observe daylight saving time on tribal lands), Hawaii, American Samoa, Guam, the Northern Mariana Islands, Puerto Rico and the United States Virgin Islands do not observe daylight saving time.